This invention relates generally to improved processes for preparing mixed squaraine compositions of matter, and more specifically the present invention is directed to processes for obtaining mixed squaraine compositions of enhanced photosensitivity by accomplishing the reaction in the presence of fluoroaniline compositions. In one embodiment of the present invention there is provided a mixture of squaraine composition products, especially bis[4-N,N-dimethyl-2-methyl phenyl]squaraine doped with N,N-dimethyl-3-fluoroaniline squaraines, of enhanced photosensitivity by the reaction of squaric acid, and an aromatic amine in the presence of a fluoroaniline, particularly N,N-dimethyl-3-fluoroaniline. The squaraine compositions resulting from these processes are useful for incorporation into layered photoresponsive imaging members wherein, for example, the sensitivity thereof can be varied or enhanced. These members are thus responsive to visible light, and infrared illumination needed for laser printing, wherein gallium arsenide diode lasers are selected. Specific photoresponsive devices or imaging members envisioned can, for example, contain situated between a photogenerating layer, and a supporting substrate, a photoconductive composition comprised of the squaraine compositions prepared in accordance with the process of the present invention.
Photoconductive imaging members with specific squaraine compositions, particularly hydroxy squaraines, are known. Also disclosed in the prior art are photoresponsive devices with photogenerating layers and transport layers, reference U.S. Pat. No. 4,265,990. Examples of photogenerating layers disclosed in this patent include trigonal selenium, and phthalocyanines. Transport layers that may be selected are comprised of certain diamines dispersed in an inactive resinous binder composition. Moreover, the use of certain squaraine pigments in photoresponsive imaging devices is disclosed in U.S. Pat. No. 4,414,639, the disclosure of which is totally incorporated herein by reference, wherein there is described an improved photoresponsive device comprised of a substrate, a hole blocking layer, an optional adhesive interface layer, an inorganic photogenerating layer, a photoconductive composition capable of enhancing or reducing the intrinsic properties of the photogenerating layer, and a hole transport layer. As photoconductive compositions for this device, there can be selected various squaraine pigments, including hydroxy squaraine compositions. Additionally, there are disclosed in U.S. Pat. No. 3,824,099 certain photosensitive hydroxy squaraine compositions. According to the disclosure of this patent, the squaraine compositions are photosensitive in normal electrostatographic imaging systems.
In other copending applications, there is described the use of novel squaraine compositions of matter, inclusive of bis-9-(8-hydroxyjulolidinyl)squaraines as imaging members. One of the members disclosed is comprised of a supporting substrate, a hole blocking layer, an optional adhesive interface layer, an inorganic photogenerating layer, a photoconducting composition layer capable of enhancing or reducing the intrinsic properties of the photogenerating layer, and comprised of the novel julolidinyl squaraine materials disclosed in the copending application, and a hole transport layer.
Also disclosed in U.S. Pat. No. 3,617,170 are optically sensitized photoconductive layers which preferably contain zinc oxide as a photoconductor, the sensitivity of which remains unchanged as a result of storage, in view of the presence of 1,3 or 1,2-squaric acid methine dyes of the formula as illustrated in column 1, beginning at line 35; while U.S. Pat. No. 3,824,099, discloses sensitive xerographic devices with a charge generating layer comprised of a squaric acid methine dye, and a charge transport layer of a triarylpyrazoline compound.
Processes for preparing squaraine compositions generally involve the reaction of squaric acid with an aromatic amine. Thus, for example, the novel julolidinyl squaraine compositions disclosed in the referenced copending application are prepared by the reaction at a temperature of from about 50 degrees Centigrade to about 130 degrees Centigrade of an aromatic amine and squaric acid, in a molar ratio of from about 1.5:1 to 3:1, in the presence of a mixture of an aliphatic alcohol and an optional azeotropic cosolvent. About 200 milliliters of alcohol per 0.1 mole of squaric acid are used, while from about 40 milliliters to about 4,000 milliliters of azeotropic material are selected. Illustrative examples of amine reactants include 8-hydroxyjulolidine, while examples of aliphatic alcohols selected are 1-butanol. Azeotropic materials used include aromatic compositions inclusive of benzene and toluene.
There is also disclosed in copending application U.S. Ser. No. 570,563, entitled Processes for the Preparation of Squaraine Compositions, the disclosure of which is totally incorporated herein by reference, a process for the preparation of photoconductive squaraine compositions wherein the known squaric acid reaction is accomplished in the presence of a phenol or a phenol squaraine. As disclosed in the referenced copending application, there is provided an improved process for the preparation of squaraine compositions which comprises reacting at an effective temperature and in the presence of an aliphatic alcohol and an optional azeotropic compound squaric acid, an aromatic amine, and a compound selected from the group consisting of phenols, or phenol squaraines. Moreover, there is disclosed in copending application U.S. Ser. No. 557,795, entitled Novel Squaraine Systems, the disclosure of which is totally incorporated herein by reference, a process for synthesizing novel unsymmetrical squaraine compositions wherein there is formed a mixture of squaric acid, a primary alcohol, a first tertiary amine, and a second tertiary amine.
Additionally, there is disclosed in another copending application U.S. Ser. No. 557,796, entitled Process for Squaraine Compositions, the disclosure of which is totally incorporated herein by reference, a squaraine process wherein there is reacted a dialkyl squarate and a N,N-dialkylaniline in the presence of an acid catalyst, at a temperature of from about 80.degree. Centigrade to about 160.degree. Centigrade, in the presence of aliphatic solvents, such as methanol, ethanol, propanol, butanol and the like.
While the above processes for preparing squaraine compositions are suitable for their intended purposes, there continues to be a need for other processes wherein photoconductive squaraine compositions can be prepared. Additionally, there remains a need for simple, economical processes for preparing squaraine compositions wherein the products obtained contain dopants therein. Although it is not desired to be limited by theory, it is believed that the presence of dopants in the squaraine compositions resulting from the process of the present invention causes the photosensitivity to increase. Furthermore, there continues to be a need for the preparation of squaraine compositions of enhanced photosensitivty when these compositions are selected for layered photoresponsive imaging devices. Moreover, there is a need for processes for effecting preparation of certain squaraine compositions of enhanced photosensitivity, wherein the resulting products when incorporated into imaging members exhibit excellent dark decay and high charge acceptance values. Additionally, there continues to be a need for the preparation of mixed squaraine compositions, particularly certain bis-phenyl squaraines doped with specific N,N-dialkyl fluoroaniline squaraines, which compositions are not only photoactive but are free of mutagenic activity. Additionally, there continues to be a need for novel squaraine compositions with increased blue wavelength response and better cycling characteristics.